Discharge tube apparatus

ABSTRACT

Electrically parallel discharges induced within a flash tube containing an inert gas at low pressure provide a compact source of radiation suitable for optical purposes. The discharges result from potential differences established between pairs of an array of three or more electrode pairs contained within the tube and arranged substantially symmetrically about a central axis. The electrode pairs are energizable independently of one another. Because of the magnetic forces between the discharges and the symmetry of the electrodes, the discharges are attracted to one another and form a substantially stable plasma which does not contact the tube walls and comprises a compact radiation source.

United States Patent 1 1 Giannini Apr. 2, 1974 DISCHARGE TUBE APPARATUS [76] Inventor: Gabriel M. Giannini, 79-8ll i Karl saalbach Avenue 54, Indio, Calif 92201 Assistant Exammer-ll1chard A. Rosenbergen Attorney, Agent, or FirmFraser and Bogucki [22] Filed: Oct. 6, 1972 1 pp 295,568 57 ABSTRACT Rela'ed AllPlication Data Electrically parallel discharges induced within a flash [60] Continuation-impart of Ser. No. 234,035, March 13, tube containing an inert gas at low pressure provide a 1972, which is a division of Se No. 28,5 6, y compact source of radiation suitable for optical pur- 28, 1969, 3,651,366- poses. The discharges result from potential differences established between pairs of an array of three or more U-S. electrode pai contained within the tube and ar- 313/224 315/235 ranged substantially symmetrically about a central j 61/80, j 61/92, 41/00 axis. The electrode pairs are energizable indepenof Search dently of one another Because of the magnetic forces 33/33, 184, i 325 between the discharges and the symmetry of the electrodes, the discharges are attracted to one another and References Cited form a substantially stable plasma which does not UNITED STATES PATENTS contact the tube walls and comprises a compact radia- 2,264,081 11/1941 Jost et a] 315 52 tion Source- 2,s43,s01 7/1958 Krefft l. 313 184 x 3,090,893 5/1963 Reaney 313 217 x 13 Clams, 6 D'awmg -20 CAPACITOR BANK CAPACITOR BANK 2e 2s 14%; 1e 55 331 {as 50 POWER SUPPLY PATENTEDAPR 2:914

SHEET 1 BF 2 CAPACITOR BANK CAPACITOR BANK CAPACITOR BANK POWER SUPPLY DISCHARGE TUBE APPARATUS The present application for patent is a continuationin-part of application, Ser. No. 234,035 filed Mar. 13, 1972, which in turn is a divisional application of application, Ser. No. 828,526 filed May 28, 1969 now issued as US. Pat. No. 3,651,366.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to systems for producing compact radiation sources comprising rapidly repeatable pulses of high intensity and short duration, as well as energy-releasing events of longer duration, by means of discharges within a gas-filled container, and relates particularly to flash tubes for producing flashes of visible, infrared, or ultraviolet radiation for photographic purposes.

2. Description of the Prior Art Existing discharge tubes used for illumination, though generally satisfactory for many purposes, have exhibited several unfavorable aspects particularly where high performance is required. Illumination emanating from such flash tubes is generally unsatisfactory for precise optical use since the light sources which they provide comprise rather extended plasmas within the tube and differ substantially from the essentially point light source ideally required for high-precision focusing and other optical operations. The diffused nature of the plasma in such tubes results in another drawback, namely, the tendency of the plasma to come into contact with the walls of the tube with a consequent relatively rapid deterioration of the walls and diminution of the useful life of the tube. Another unfavorable aspect of this tendency of existing flash tubes is that much of the energy of the plasma may be dissipated in heating the tube walls rather than in producing desired illumination. Previous attempts to solve the problem of plasma contact with tube walls have taken the direction of simply enlarging the tubes. This approach, however, has the drawback of aggravating the problem of discharge inductance which has a particularly adverse effect on the attainable brevity of flashes.

There has therefore been a recognized-but previously unfulfilled need for flash tubes which provide a relatively compact source of illumination and in which the plasma makes little or no contact with the tube walls and at the same time have sufficiently low inductance to permit flashes of short duration.

SUMMARY OF THE INVENTION The purposes and objectives of the invention are realized by a gas-filled tube having at least three pairs of electrodes symmetrically disposed about a central axis and connected to external circuitry so that every elec trode pair is energized independently of every other electrode pair.

A particular arrangement in accordance with the invention comprises an elongated flash tube having a longitudinal axis, a set of at least three emitter electrodes disposed at the vertices of an imaginary equilateral triangle centered about the axis and a set of collector electrodes arrayed in the same manneras the emitters and disposed opposite thereto, to form at least three discharge electrode pairs. Each electrode pair is coupled to a separate capacitor bank. Another particular arrangement comprises a spherical tube in which groups of emitter and collector electrodes are disposed at opposite poles of the sphere and symmetrically about a diameter between the poles.

An aspect of the invention is that the discharges due to breakdown potential differences between the electrode pairs are parallel and thus subject to the pinch effect, that is, the attractive force which exists between parallel electric currents due to the interaction of each current with the magnetic field of the other. Thus, the discharges tend to move toward one another and form a substantially compact light-source plasma within the interior of the tube, thereby eliminating the problem of diffuseness of light source.

Another aspect of the invention is in the symmetrical placement of the electrode pairs. This placement provides a plasma which is substantially stable geometrically, that is, tending to have a substantially constant location within the tube. This characteristic results in a superior source of illumination and in prevention of contact between the walls and the plasma.

A further aspect of the invention is in the separate energization of the electrode pairs. This type of energithe discharges tend to cancel. This facilitates rapid flashing where such flashing is desirable.

BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of the invention may be had from a consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view, somewhat simplified, of a particular flash tube in accordance with the invention;

FIG. 2 is a cross-sectional view of the flash tube of FIG. 1 taken along the plane 2-2 thereof;

FIG. 3 is a schematic representation of a system including electrical circuitry associated with a flash tube in accordance with the invention;

FIG. 4 is a perspective view, somewhat simplified, of another embodiment of the invention comprising a substantially spherical configuration; and

FIGS. 5 and 6 comprise end views of the embodiment of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION As depicted in FIG. 1, a discharge tube 10 in accordance with the invention comprises a housing or envelope 11 transparent to a selected spectral range which may include ultraviolet, visible, or infrared and having a generally elongated configuration and a central axis of symmetry 12 (indicated in phantom). The housing 11 contains an inert gas, such as krypton, which provides the type of radiation desired upon discharge. The tube 10 contains a system of electrodes comprising two sets of electrodes 14, 16 comprising a group of emitters 14A, 14B, 14C and a group of collectors 16A, 16B, 16C, respectively.

Placement of the electrode sets l4, 16 is symmetrical about the axis 12, as best seen in FIG. 2. The electrode sets l4, 16 are disposed at substantially the vertices of an imaginary equilateral triangle centered at the axis 12, that is, the electrodes are spaced at equal intervals of 120 along a common circle whose center lies on the axis 12. Each electrode of each set is disposed opposite its paired counterpart in the other set (electrodes designated by the same letter suffix comprise the pairs, e.g., electrodes 14A and 16A form a pair). Thus, discharges passing between electrodes of the two sets will follow substantially parallel paths.

Electrode sets 14, 16 are connected to external circuitry 18, as seen in. FIG. 3. Circuitry 18 includes capacitor banks 20, 22, 24 separately coupled to the individual electrode pairs 12A, 16A; 14B, 16B; 14C, 16C, respectively, and to a power supply 25. This arrangement in conjunction with the symmetrical placement of the electrode sets 14, 16, permits the formation of plasmas resulting from discharges which are substantially stable geometrically. Separate energization of individual electrode pairs avoids the asymmetries which would result from charging the electrode pairs from a common source and would cause geometrical asymmetries of the plasma as well as cross-over discharges.

Circuitry 26 triggers the capacitor banks 20, 22 and 24 andincludes a transformer 28 having its primary winding connected in series with an ignition switch 30 and generates an ignition pulse which may be applied from the secondary winding of the transformer 28 to an igniter electrode 32 via an ignition circuit connected to a tap in a bleeder network comprising resistors 33 coupled to the power supply 25. The igniter electrode 32 is disposed within the tube and may be used to initiate a discharge within the tube 10, which discharge transfers to the major discharge paths between the electrode sets 14, 16. Resistors 34, 35, 36 are disposed in series legs between the power supply 25 and the capacitor banks 20, 22 and 24, respectively.

In operation, as shown in FIG. 3, discharges 37 exist between pairs opposed electrodes within the sets l4, 16. These discharges may vary in duration from essentially continuous discharges to extremely brief flashes. Though the interval between the electrode pairs is such that in the absence of electromagnetic phenomena the discharges following those paths would be substantially parallel, the electromagnetic interaction of every discharge with the magnetic fields of the other discharges causes a pinching Le. a drawing together of the discharges and of the resulting plasma. This pinch is due to the attractive forces exerted by the magnetic fields of every one of the discharges upon every one of the other discharges. Thus, the plasma resulting from the discharges tends to form a compact illumination source at 37A. Utilizing the principles and techniques of magnetohydrodynamics, it has been discovered that plasmas stemmingfrom dischargesbetween substantially three dimensionally symmetrically arrayed electrode pairs tend to be spatially stable. Thus, the combination of the electromagnetic effects and magnetohydrodynamic effects utilized by the invention provides a compact plasma which tends not to drift generally relative to the discharge tube and particularly does not tend to contact the housing of the tube.

Symmetrical placement of the emitting and collecting electrode sets 14 and 16 as shown is an example of arrangements in accordance with the invention. Other symmetrical arrangements of electrode sets are also possible within the scope of the invention. Also in accordance with the invention an electrode pair may be disposed along, as well as about, a line of symmetry.

Although it is preferable to have the same gap length between all of the electrode pairs in a given tube, it will be appreciated that these lengths may be made different. For example, the gap separating paired electrodes 14A and 16A may be somewhat shorter than that separating electrodes 14B and 16B.

A further specific example of a discharge tube in accordance with the invention is shown in FIGS. 4-6 in which a discharge tube having an envelope 38 of generally spherical form is depicted. The envelope 38 has an axis 39 coinciding with a diameter of the envelope. The axis 39 intersects the envelope at diametrically opposed points 40 and 42 about which are disposed electrode sets 44 and 46, respectively.

With particular reference to FIG. 5, taking the electrodes about point 40 by way of example (the array about point 42 is identical), four'electrodes 44A-44D are arranged at equal intervals about an imaginary inner circle 48 concentric of the point 40. Eight electrodes 44E-44L are disposed at equal intervals along a larger imaginary circle 50 also concentric of the point 40. The array also includes a central electrode 44M coinciding with the axis 39.

The electrodes 44A-44M are paired with identically arranged electrodes 46A-46M about and at the point 42 (FIG. 6), electrode 44A being paired with electrode 46A, 44B with 46B, and so forth, in the fashion already described in connection with previous embodiments. It

will further be seen that all of the electrodes are oriented in parallelism with the central axis 39 and in further similarity with previous embodiments, each pair of electrodes is connected to an independent source of electrical power (not shown) which may be of the kind discussed in connection with FIG. 2.

It will be noted that the respective electrode arrays in FIGS. 4-6 are symmetrical with respect to any plane including any electrode pairs and the axis 39. This type of symmetry is not required, however, symmetry of each set of electrodes about a common axis being sufficient to provide the benefits of the invention. Furthermore, the specific numbers of electrodes and electrode pairs may vary from that shown in accordance with particular design and performance requirements. What is claimed is:

1. Flash tube apparatus having a long useful life and providing a concentrated, high energy, high intensity light source for precise optical uses comprising:

a transparent outer envelope containing an inert gas;

a system of electrodes disposed within the outer envelope and including at least a first and second set of electrodes, each set comprising at least three electrodes, the electrodes of the first set comprising a three-dimensional array positioned symmetrically about a first point, the second set of electrodes comprising a three-dimensional array positioned symmetrically about a second point and opposite the first set of electrodes so that an imaginary line between every electrode of the first set and the nearest electrode of the second set is substantially parallel to imaginary lines from each of the at least two other electrodes of the first set to the nearest electrode of the second set.

2. The invention as set forth in claim 1 wherein the outer envelope has an elongated shape and an axis of symmetry along the longitudinal dimension thereof and wherein said imaginary lines connecting the electrode sets are substantially parallel to said axis of symmetry of the outer envelope.

3. The invention as set forth in claim 1 further including means for developing potential difference between every pair of electrodes along said imaginary line, said means developing said potential difference separately for every said electrode pair.

4. A flash tube apparatus having superior durability and providing a concentrated source of high energy, high intensity radiation suitable for precise optical uses comprising:

a housing transparent to a selected spectral range and containing a selected inert gas;

a system of electrodes comprising at least three pairs of electrodes including emitter electrodes and collector electrodes, the pairs being arranged symmetrically in a three-dimensional array about an imaginary line of symmetry so that straight lines between the respective pairs are substantially parallel to the line of symmetry; and

means coupled to said electrode pairs for inducing discharge between the electrodes of every pair, said discharge-inducing means of each pair being independent of the discharge-inducing means of every other pair, said discharges being mutually attracted to each other by the pinch effect to form a compact, stable, centrally positioned, high energy density radiation source.

5. The invention as set forth in claim 4 wherein the emitter electrodes of said at least three pairs of electrodes comprise a first set of electrodes and said collector electrodes comprise a second set of electrodes, said first set of electrodes being arrayed at vertices of an imaginary equilateral triangle centered at a first point on said imaginary line of symmetry, and said second electrode set being arrayed at vertices of a second imaginary equilateral triangle centered at a second point on the line of symmetry.

6. The invention as set forth in claim 4 wherein said means for inducing discharges between said pairs of electrodes comprises a capacitor bank connected across each electrode pair, said capacitor banks being coupled in parallel.

7. The invention as set forth in claim 6 further including igniting means disposed within said housing for igniting said discharges between said pairs of electrodes, said igniting means being coupled parallel to said capacitor means.

8. A system for producing a high energy density, concentrated radiation source suitable for precise optical purposes comprising:

an outer envelope transparent to radiation and containing a selected inert gas whose discharge energy release provides the desired illumination, said envelope having a longitudinal axis of symmetry; and

electrode means arrayed symmetrically about said axis to define at least three substantially parallel discharge paths within said outer envelope, said discharge paths being symmetrically disposed at substantially equal angular intervals about said axis. 9. A tube for providing a concentrated source of high energy, high intensity radiation comprising:

a transparent housing having a generally spherical configuration and containing an inert gas;

electrode means disposed within said housing and arrayed substantially symmetrically about a diameter of said spherical housing, said electrode means comprising at least three first pairs of electrodes, each set pair comprising an emitter electrode and a collector electrode, said emitter electrodes being symmetrically arrayed at equal angular intervals along a first circle centered on said diameter, said collector electrodes being symmetrically arrayed at equal angular intervals along a second circle centered on said diameter and equal in diameter and opposite to said first circle; and

a discharge-inducing means coupled to each pair of electrodes, such discharge-inducing means of each pair of electrodes being independent of the discharge-inducing means of every other pair of electrodes.

10. The invention as set forth in claim 9 further including at least three second pairs of electrodes, each said pair comprising an emitter electrode and a collector electrode, said emitter electrodes of said second pairs being symmetrically arrayed at equal angular intervals along a third circle centered on said diameter, said collector electrodes of said second pairs being symmetrically arrayed at equal angular intervals along a fourth circle centered on said diameter and equal in diameter and opposite to said third circle.

11. The invention as set forth in claim 10 further including a pair of electrodes disposed along said diameter.

12. A luminous source comprising:

an outer envelope containing an inert gas;

a plurality of sets of electrodes, every set comprising a group of emitter electrodes and a group of collector electrodes said groups comprising at least three electrodes each, the emitter group and collector group of every set being arrayed opposite each other and symmetrically along the perimeter of a pair of imaginary circles in substantially parallel planes, the planes of the imaginary circles of the groups for every set being substantially parallel to the planes of the imaginary circles for the groups of said other sets.

13. The invention as set forth in claim 12 further including means for separately energizing every pair of electrodes. 

1. Flash tube apparatus having a long useful life and providing a concentrated, high energy, high intensity light source for precise optical uses comprising: a transparent outer envelope containing an inert gas; a system of electrodes disposed within the outer envelope and including at least a first and second set of electrodes, each set comprising at least three electrodes, the electrodes of the first set comprising a three-dimensional array positioned symmetrically about a first point, the second set of electrodes comprising a three-dimensional array positioned symmetrically about a second point and opposite the first set of electrodes so that an imaginary line between every electrode of the first set and the nearest electrode of the second set is substantially parallel to imaginary lines from each of the at least two other electrodes of the first set to the nearest electrode of the second set.
 2. The invention as set forth in claim 1 wherein the outer envelope has an elongated shape and an axis of symmetry along the longitudinal dimension thereof and wherein said imaginary lines connecting the electrode sets are substantially parallel to said axis of symmetry of the outer envelope.
 3. The invention as set forth in claim 1 further including means for developing potential difference between every pair of electrodes along said imaginary line, said means developing said potential difference separately for every said electrode pair.
 4. A flash tube apparatus having superior durability and providing a concentrated source of high energy, high intensity radiation suitable for precise optical uses comprising: a housing transparent to a selected spectral range and containing a selected inert gas; a system of electrodes comprising at least three pairs of electrodes including emitter electrodes and collector electrodes, the pairs being arranged symmetrically in a three-dimensional array about an imaginary line of symmetry so that straight lInes between the respective pairs are substantially parallel to the line of symmetry; and means coupled to said electrode pairs for inducing discharge between the electrodes of every pair, said discharge-inducing means of each pair being independent of the discharge-inducing means of every other pair, said discharges being mutually attracted to each other by the pinch effect to form a compact, stable, centrally positioned, high energy density radiation source.
 5. The invention as set forth in claim 4 wherein the emitter electrodes of said at least three pairs of electrodes comprise a first set of electrodes and said collector electrodes comprise a second set of electrodes, said first set of electrodes being arrayed at vertices of an imaginary equilateral triangle centered at a first point on said imaginary line of symmetry, and said second electrode set being arrayed at vertices of a second imaginary equilateral triangle centered at a second point on the line of symmetry.
 6. The invention as set forth in claim 4 wherein said means for inducing discharges between said pairs of electrodes comprises a capacitor bank connected across each electrode pair, said capacitor banks being coupled in parallel.
 7. The invention as set forth in claim 6 further including igniting means disposed within said housing for igniting said discharges between said pairs of electrodes, said igniting means being coupled parallel to said capacitor means.
 8. A system for producing a high energy density, concentrated radiation source suitable for precise optical purposes comprising: an outer envelope transparent to radiation and containing a selected inert gas whose discharge energy release provides the desired illumination, said envelope having a longitudinal axis of symmetry; and electrode means arrayed symmetrically about said axis to define at least three substantially parallel discharge paths within said outer envelope, said discharge paths being symmetrically disposed at substantially equal angular intervals about said axis.
 9. A tube for providing a concentrated source of high energy, high intensity radiation comprising: a transparent housing having a generally spherical configuration and containing an inert gas; electrode means disposed within said housing and arrayed substantially symmetrically about a diameter of said spherical housing, said electrode means comprising at least three first pairs of electrodes, each set pair comprising an emitter electrode and a collector electrode, said emitter electrodes being symmetrically arrayed at equal angular intervals along a first circle centered on said diameter, said collector electrodes being symmetrically arrayed at equal angular intervals along a second circle centered on said diameter and equal in diameter and opposite to said first circle; and a discharge-inducing means coupled to each pair of electrodes, such discharge-inducing means of each pair of electrodes being independent of the discharge-inducing means of every other pair of electrodes.
 10. The invention as set forth in claim 9 further including at least three second pairs of electrodes, each said pair comprising an emitter electrode and a collector electrode, said emitter electrodes of said second pairs being symmetrically arrayed at equal angular intervals along a third circle centered on said diameter, said collector electrodes of said second pairs being symmetrically arrayed at equal angular intervals along a fourth circle centered on said diameter and equal in diameter and opposite to said third circle.
 11. The invention as set forth in claim 10 further including a pair of electrodes disposed along said diameter.
 12. A luminous source comprising: an outer envelope containing an inert gas; a plurality of sets of electrodes, every set comprising a group of emitter electrodes and a group of collector electrodes said groups comprising at least three electrodes each, the emitter group and collector group of everY set being arrayed opposite each other and symmetrically along the perimeter of a pair of imaginary circles in substantially parallel planes, the planes of the imaginary circles of the groups for every set being substantially parallel to the planes of the imaginary circles for the groups of said other sets.
 13. The invention as set forth in claim 12 further including means for separately energizing every pair of electrodes. 